It is known that methacrylic acid can be produced by the vapor phase oxidation of isobutylene or methacrolein. However, saturated hydrocarbons such as isobutane, are considered inert materials and have often been used as diluents for the reactant gases when preparing unsaturated aldehydes and acids. For example, U.S. Pat. No. 3,293,290, in discussing the prior art, describes the use of low boiling alkanes as inert diluents for reactant gases such as olefins in preparing unsaturated acids.
It is known that methacrylic acid may be prepared from isobutane by direct catalytic oxidation using certain molybdenum and antimony containing catalysts. However, this process suffers from the disadvantage of a very low selectivity when converting the isobutane to methacrylic acid. The selectivity is known to be in the order of about 2% and this factor mitigates against such a process being commercially utilized because of the economics which are involved.
It is an object of this invention therefor to provide a process for the single stage oxidation of isobutane or propane to methacrylic acid or acrylic acid.
Another object of this invention is to provide such a process with a high degree of selectivity for the conversion of the alkane in the feed gas to methacrylic or acrylic acid.
Other objects and advantages will become apparent from the following more complete description and claims.